Communication systems including cellular, mobile, and other wireless communication systems transmit and receive data. In many such wireless communication systems data is carried within a channel by a carrier signal having a frequency corresponding to the center of the channel. Further, wireless communication systems may have several channels each having a carrier signal that is modulated in some manner to carry data across a wireless medium. Further, wireless communication systems may be digital communication systems that carry data as a sequence of symbols that represent data bits. Such data may be encoded to add redundancies to the data stream. Encoding the data provides a robust communication system that allows the RF receiver to recover the transmitted data even though the encoded data may have been impacted by noise, attenuation, and multipath fading due to transmitting the data across the wireless medium. Further, the encoded data may also be impacted by distortion due to components of the RF receiver (e.g., mixers, automatic again control (AGC) attenuators/amplifiers, analog-to-digital converters, etc.). The modulation scheme may comprise a plurality of symbols used to alter a magnitude, phase, or both, of a carrier signal, where each symbol represents a sequence of bits (e.g., each symbol in a Quadrature Phase Shift Keying (QPSK) modulation scheme is one of four carrier phases representing two bits).
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.